The present invention is directed to a technique and circuitry for minimizing the number of electrical input terminals to a monolithic integrated electrical structure, which structure includes memory capabilities. More specifically, the present invention is directed to the merging of the functions associated with the operation of such a monolithic integrated electrical device so as to permit the reduction of electrical conductors and/or pins which connect the device in a system so as to, in turn, permit a substantially larger number of such devices to be placed in a given area.
Substantial research effort is continually expended by manufacturers of monolithic integrated circuits to substantially reduce the physical size and volume of monolithic integrated circuits in order to provide both increased circuit density and decreased cost, whereby the cost per bit of storage in high access speed static memories constructed utilizing such devices is comparable to the cost per bit of storage provided by relatively low access speed dynamic memories such as, for example, magnetic discs, drums, tapes, and the like. Even though integrated circuits (IC's) and large-scale integrated circuits (LSI's) have increased the density of electronic circuits per se substantially, the overall size and volume of the package thereof is still much too large to achieve the same relative packing density by high-speed static memories as achieved by relative low-speed dynamic magnetic memories. In the present state of the art, connections to these circuits are generally made by bonding leads to pads which are fixed on the chip supporting the integrated circuit and by bonding the leads to package tabs. The package houses the integrated circuit and the tabs project through the package. The tabs are electrically connected to conductors, which conductors are bonded to a circuit board and are routed on the circuit board to interconnect the package IC in its circuit environment. Each conductor occupies an area upon the board. The area occupied by the conductors detracts from the area occupied, or capable of being occupied, by an IC device, and therefore substantially reduces the density of the electronics on the circuit board. A reduction in the number of conductors on the board will, in turn, increase the area onto which additional IC devices may be positioned. An increase in IC devices in a particular area will of course increase the density of the IC's. Increased density is particularly important when dealing with memory devices in that the greater the density, the greater the number of memory bits that can be feasibly designed into a system having fixed physical constraints on size.
The present invention deals with the problem of increasing memory density by substantially decreasing the number of conductors and associated pins that are needed to interface to an integrated circuit type memory device.